U.S. patent number 5,136,556 [Application Number 07/783,663] was granted by the patent office on 1992-08-04 for wide bandwidth barrel stave projector.
This patent grant is currently assigned to The Unites States of America as represented by the Secretary of the Navy. Invention is credited to Robert J. Obara.
United States Patent |
5,136,556 |
Obara |
August 4, 1992 |
Wide bandwidth barrel stave projector
Abstract
An underwater acoustical projector has its barrel staves located
radially tward of a piezoelectric ceramic driver. The barrel staves
are in an hour glass arrangement. The cross-sectional arrangement
of the barrel staves is circular at both the top and bottom of the
hour glass forming elliptical cross-sections of varying
eccentricity between said top and bottom of said staves. The
cross-section of greatest eccentricity is located midway between
the top and bottom of said staves. The cross-section of greatest
eccentricity is located midway between the top and bottom of the
barrel staves. This forms a projector with a varying radius of
curvature in each of the four 90.degree. quadrants around the axis
of the projector. This yields large changes in the resonant
frequency.
Inventors: |
Obara; Robert J. (Portsmouth,
RI) |
Assignee: |
The Unites States of America as
represented by the Secretary of the Navy (Washington,
DC)
|
Family
ID: |
25130029 |
Appl.
No.: |
07/783,663 |
Filed: |
October 28, 1991 |
Current U.S.
Class: |
367/163; 310/337;
367/158 |
Current CPC
Class: |
B06B
1/0611 (20130101); G10K 9/121 (20130101) |
Current International
Class: |
B06B
1/06 (20060101); G10K 9/12 (20060101); G10K
9/00 (20060101); H01V 007/00 () |
Field of
Search: |
;310/337
;367/155,157,158,159,165,166,163 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Steinberger; Brian S.
Attorney, Agent or Firm: McGowan; Michael J. Lall; Prithvi
C. Oglo; Michael F.
Government Interests
STATEMENT OF GOVERNMENT INTEREST
The invention described herein may be manufactured and used by or
for the Government of the United States of America for governmental
purposes without the payment of any royalties thereon or therefor.
Claims
What is claimed is:
1. A barrel stave acoustical projector comprising:
at least one plate located at the top of said acoustical
projector;
at least one plate located at the bottom of said acoustical
projector;
a driver located between said at least one plate located at the top
of said acoustical projector and said at least one plate located at
the bottom of said projector;
electrical means for providing an electrical signal to said driver;
and
a plurality of staves forming an hourglass shape with the
cross-sectional shape of the arrangement of said staves forming a
circle at the top and bottom of said staves and elliptical cross
sections of varying eccentricity between said top and bottom of
said staves, said staves located radically outward of said driver,
said staves are further arranged so that within said staves a plane
orthogonal to the axis of the hourglass shape located a
predetermined distance between said top and said bottom of said
staves has both an area that is smaller than that in any other
plane orthogonal to the axis of said hourglass shape and an
elliptical eccentricity that is larger than that in any other plane
orthogonal to the axis of said hourglass shape.
2. A barrel stave acoustical projector according to claim 1 wherein
said plane having both said area that is smaller than that in any
other plane orthogonal to the axis of said hourglass shape and said
elliptical eccentricity that is larger than that in any other plane
orthogonal to the axis of said hourglass shape being formed
substantially equal distance between said top and bottom of said
staves.
3. A barrel stave acoustical projector according to claim 2 wherein
said driver further comprises a stack of piezoelectric ceramic
disks.
4. A barrel stave acoustical projector according to claim 3 further
comprising a stress bolt connected to said at least one plate
located at the top of said acoustical projector and said at least
one plate located at the bottom of said acoustical projector, said
stress bolt extending through and being coaxial with said
piezoelectric ceramic disks.
5. A barrel stave acoustical projector according to claim 4 further
comprising a rubber boot extending over said staves and bonded to
said at least one plate located at the top of said acoustical
projector and said at least one plate located at the bottom of said
acoustical projector.
6. A barrel stave acoustical projector according to claim 5 further
comprising ethylene glycol being spread between said staves and
said rubber boot.
7. A barrel stave acoustical projector according to claim 6 further
comprising:
said at least one plate located at the top of said acoustical
projector being an end cap and a cover; and
an O-ring providing a water tight seal between said end cap and
cover.
Description
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to sound radiation. More particularly
it concerns an improvement in an underwater barrel stave acoustical
projector that has use as a mobile target capable of simulating the
spatial extent of a submarine. The barrel stave projector is a
flextensional device that drives a series of concave staves in the
radial direction by the application of a force in the axial
direction produced by a stack of piezoelectric ceramic rings in
response to an electrical input. Thus, the projector essentially
operates as a mechanical amplifier, coupling the longitudinal
vibration of a piezoceramic driver to the transverse vibration of a
passive shell comprised of a plurality of barrel staves.
(2) Description of the Prior Art
In prior art systems a barrel stave projector used identical staves
made of curved flexible bars arranged so that the profile of the
projector is similar to an hourglass which is circular in
horizontal cross-section at all points from the top to the bottom
thereof. This configuration provided a very limited range of
resonant frequency for such a projector.
SUMMARY OF THE INVENTION
Accordingly, it is a general purpose and object of the present
invention to provide an improved flextensional device for
simulating the active characteristics of submarines. It is a
further object that the device has a broad range of frequencies. An
additional object is that the device be capable of being towed
underwater as part of an array of projectors.
These objects are accomplished with the present invention by
modifying a typical barrel stave projector that is suitable for
underwater use by varying the radius of curvature of the staves so
that a different type of hourglass shape is formed by the
arrangement of the staves. The hourglass formed in subject device
has a circular cross-section along the horizontal planes at the top
and bottom thereof and has an elliptical cross-section along the
horizontal planes through points between the top and the bottom.
The elliptical horizonal cross-section at the midway point has the
highest value of eccentricity.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of a barrel stave projector in
accordance with the present invention;
FIG. 2 is a view of the area of the staves taken along the line
2--2 of FIG. 1; and
FIG. 3 is a view of the top and bottom surfaces of the staves of
FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1 there is shown a cross-sectional view of a
barrel stave projector 10. A piezoelectric ceramic stack 12 is
comprised of a plurality of elements 14. The number of elements 14
and their diameter can vary. Electrical leads 16 are connected to
the elements 14. A stress bolt 18 is used to ensure that the stack
12 is never subject to tensile stresses. The projector 10 has a
full complement of eight staves 20 mounted on upper and lower
octagonal end caps 22 and 24, respectively by means of screws 25.
The stress bolt 18 passes through the center of the elements 14
holding the end caps 22, 24, in place. The upper end cap 22 holds a
pair of electrical terminals 26. A cover plate 28 is secured to
upper end cap 22 by means of bolts 29. An O-ring seal 30 is secured
between the cover plate 28 and the upper end cap 22. An electrical
connector 32 that receives the electrical signals that are applied
to the elements 14 is secured to cover plate 28. A rubber boot 34
is stretched over the staves 20 and bonded to the end caps 22, 24
with bands 35 to act as a seawater seal. A light coat of ethylene
glycol 36 is used between the staves 20 and the boot 34 to
eliminate trapped air.
The assembly of staves in the projector 10 form an hour glass shape
with the ends of the structure being circular in shape and the
middle of the structure at its thinnest part forming an ellipse.
This is shown in FIGS. 2 and 3. FIG. 2 taken along the line 2--2 of
FIG. 1 shows the thinnest cross-sectional area to be elliptical.
FIG. 3 shows the area of the top and bottom of the staves 20 to be
circular. Elliptical cross-sections of varying eccentricity are
formed at the horizontal planes between the top and bottom of the
projector. The middle of the hour glass arrangement where the
thinnest cross-section is located has the elliptical cross-section
of largest eccentricity. The new projector has a wide bandwidth of
resonant frequency for its operation.
There has therefore been described a barrel stave sound projector
that has a radius of curvature that varies continuously between
fixed values as the angle about the axis of the projector varies.
This enables the projector to yield large changes in the range of
resonant frequency.
It will be understood that various changes in the details,
materials, steps and arrangement of parts, which have been herein
described and illustrated in order to explain the nature of the
invention, may be made by those skilled in the art within the
principle and scope of the invention as expressed in the appended
claims.
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